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A hungry fish can kill prey with a quick bite. That is, of course, if its prey hasn't already died of fright. Take tasty dragonflies. The mere presence of predators—even caged ones—is enough to scare dragonflies to death, according to a study in the journal Ecology. [Shannon J. McCauley, Locke Rowe, and Marie-Josée Fortin, "The deadly effects of ‘nonlethal’ predators"]
Researchers collected wild dragonfly larvae, and placed them in tanks with fish or insect predators. The larvae could see and smell their hunters—but were kept safe by underwater cages. After two months, the researchers took a head count—and found that dragonfly larvae sharing quarters with their killers were two to four times as likely to die off, compared to counterparts living in predator-free waters. And they had slimmer chances of surviving metamorphosis, too.
The authors suggest a couple reasons why. First, prey tend to make fewer forays for snacks when predators are lurking around, so they may not be as nutritionally fit. And previous studies have shown that the presence of predators ups stress levels in prey, weakening their immune systems and making them more vulnerable to disease—and death.
As if being eaten wasn't enough to worry about, looks can kill too.
—Christopher Intagliata
[The above text is a transcript of this podcast.]
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6 Comments
Add CommentThe research is about larvae of dragonflies and not about that insect when adults! This is indisputable. Ok? Ok!
Reply | Report Abuse | Link to thisBy the bye, in our childhood, me and my friends, we called those flying insects *helicopters*.
Chess players utilize the "psychology of chess", which is a discipline within the game of chess, itself, to both strengthen their own chess game, resist psychological intimidation by their opponents, and psychologically intimidate and stress out their opponents to gain the advantage of the game.
Reply | Report Abuse | Link to thisWe called them "mosquito hawks"
Reply | Report Abuse | Link to thisThey're also called "bee butchers".
Reply | Report Abuse | Link to thisWell, I just wonder why sometimes when you are chased by a beast, you can run much faster than ever before, however, in other occasion when you are walking along a single-log bridge with crocodiles swimming below, you cannot keep your balance, even though you can easily pass the bridge when you are told no crocodile is swimming below at the beginning. Stress sometimes can stimulate your potential, whereas inhibit your performance some other time.
Reply | Report Abuse | Link to thisThis is also evident in the way that wolves will stalk a single buffalo. They'll single one out, and just hang around it, circling and psyching the buffalo out and even though they are not preventing it from eating or carrying out vital needs for survival the psychological warefare of having the predators around all the time and being without the protection of a herd around it weakens the animal and can make it more succeptible to disease. It can take weeks before the wolves attack. The 'Wolf' episode of David Attenborough's Wildlife Specials showcases a hunt nicely. Thanks for the great read!
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